In 2008 the building of a first windmill park some 30km off the Belgian North Sea coast began. Such offshore constructions represent a novel, artificial, hard substratum habitat on the Belgian continental shelf, where the sea-bottom consists mainly of sandy and muddy sediment. It is anticipated that in the coming years, several hundreds of offshore windmills will be constructed in a dedicated zone off the Belgian coast. SCUBA-based in situ techniques were used to document and sample the fouling assemblage on the hard substratum represented by the concrete foundations of the first windmills constructed in Belgian waters. Here this paper presents and discusses the results of the monitoring undertaken from February 2009 to February 2010. Despite the further offshore location and differences in substratum type, the preliminary results indicated that the overall structure of the marine biofouling assemblage at the Thornton Bank site is similar to that on the foundations of other offshore wind farms in Germany, Denmark and the Netherlands, as well as on other hard structures in the North Sea.